Controlling a pump conveying a coolant in a charging gas cooling circuit

Abstract

The invention describes is a method (27) for controlling a coolant-conveying pump (7) in a charge gas cooling circuit (3) in order to cool a charge gas (9) for an internal combustion engine, whereby the method involves: maintaining (29) an inlet temperature (51) of the charge gas (9) in a heat exchanger (13) that is configured to exchange heat between the charge gas (9) and the coolant; ascertaining (31) a target cooling output (21) on the basis of the inlet temperature (51, T21) of the charge gas (9) and on the basis of a target outlet temperature (T22.sub.target) of the charge gas (15) coming from the heat exchanger (13); determining (33) a change (23) of the target cooling output (21) over time, and providing (35) an actuation signal (25) for the pump (7) based on the target cooling output (21) and on the change (23) of the target cooling output over time.

Claims

1. A method for controlling a coolant-conveying pump in a charge gas cooling circuit in order to cool a charge gas for an internal combustion engine, whereby the method comprises: maintaining an inlet temperature of the charge gas in a heat exchanger that is configured to exchange heat between the charge gas and the coolant; ascertaining a target cooling output on the basis of the inlet temperature of the charge gas and on the basis of a target outlet temperature of the charge gas coming from the heat exchanger; determining a change of the target cooling output over time; and providing an actuation signal for the pump based on the target cooling output and on the change of the target cooling output over time.

2. The method according to claim 1, whereby providing the actuation signal involves generating a square wave signal whose duty factor is ascertained on the basis of the target cooling output and on the basis of the change of the target cooling output over time.

3. The method according to claim 1, whereby determining the change of the target cooling output over time comprises: ascertaining a first target cooling output as well as a second target cooling output that have a time interval between 10 ms and 500 ms; and determining the difference between the first target cooling output and the second target cooling output.

4. The method according to claim 3, whereby determining the change of the target cooling output over time comprises: forming a quotient from the difference and the time interval.

5. The method according to claim 1, whereby providing the actuation signal comprises: determining the time curve of the change of the target cooling output over time; low-pass filtering of the curve of the change of the target cooling output over time so that a filtered change of the target cooling output over time can be obtained; and determining the actuation signal on the basis of the target cooling output and on the basis of the filtered change of the target cooling output over time.

6. The method according to claim 5, whereby the time interval and/or a cutoff frequency of the low-pass filtering is set as a function of the ambient temperature.

7. The method according to claim 6, whereby providing the actuation signal involves: determining a first signal on the basis of the target cooling output and on the basis of the ambient temperature or on the basis of the coolant temperature, whereby the first signal rises as the target cooling output increases; determining a second signal by means of a PID controller on the basis of the difference between the target outlet temperature of the charge gas and the actual outlet temperature of the charge gas coming from the heat exchanger; determining a third signal on the basis of the filtered change of the target cooling output over time; and adding the first signal, the second signal and the third signal in order to obtain the actuation signal.

8. The method according to claim 7, whereby determining the third signal is also based on the ambient temperature, and whereby the amplitude of the third signal at negative ambient temperatures and/or at ambient temperatures above 30 C. is increased to a lesser extent than in the case of ambient temperatures between 0 C. and 20 C.

9. The method according to claim 1, whereby determining the target cooling output is also based on the mass flow of the charge gas.

10. A device for controlling a coolant-conveying pump in a charge gas cooling circuit in order to cool a charge gas for an internal combustion engine, whereby the device is configured to carry out a method according to claim 1.

11. The method according to claim 3, whereby the time interval and/or a cutoff frequency of the low-pass filtering is set as a function of the ambient temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically illustrates a charge gas cooling circuit having a device for controlling a coolant-conveying pump in the charge gas cooling circuit according to an embodiment of the present invention, which is configured to carry out a method according to an embodiment of the present invention;

(2) FIG. 2 schematically illustrates the carrying out of a method according to an embodiment of the present invention;

(3) FIG. 3 schematically illustrates modules of a method for controlling a coolant-conveying pump in a charge gas cooling circuit according to an embodiment of the present invention;

(4) FIG. 4 schematically illustrates a module that is used in a method for controlling a coolant-conveying pump in a charge gas cooling circuit according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(5) The charge gas cooling system 1 schematically shown in FIG. 1 comprises a charge gas cooling circuit 3 and a device 5 for controlling a coolant-conveying pump 7 in the charge gas cooling circuit 3 in order to cool a charge gas 9 for an internal combustion engine according to an embodiment of the present invention, whereby the device 5 is configured to carry out a method for controlling a coolant-conveying pump in a charge gas cooling circuit according to an embodiment of the present invention.

(6) The charge gas cooling circuit 3 comprises several line sections 11 in which a coolant can be conveyed in a conveying direction 14 by means of the pump 7. The conveying direction 14 can also run in the opposite direction. The charge gas cooling circuit 3 comprises a heat exchanger 13 with a line system (not depicted in detail here) in which the coolant can be conveyed. The line system of the heat exchanger 13 has a relatively large external surface area over which the (uncooled) charge gas 9 can be conveyed for purposes of heat exchange so as to yield a cooled charge gas 15, whereby some of the heat contained in the uncooled charge gas 9 is released to the coolant that is flowing through the heat exchanger 13. The coolant is further conveyed through a low-temperature cooler 17 in which, in turn, some of its heat can be released to the environment via the low-temperature cooler 17.

(7) The device 5 receives a signal 19 that indicates an inlet temperature T21 of the charge gas 9 in the heat exchanger 13. Moreover, the device 5 ascertains a target cooling output 21 on the basis of the inlet temperature T21 of the charge gas 9, a target outlet temperature T22.sub.target of the charge gas 15 coming from the heat exchanger 13, and the gas mass flow of the charge gas 9. Furthermore, the device determines a change of the target cooling output over time (especially filtered), which is designated by the reference numeral 23. Based on the target cooling output 21 and the change 23 of the target cooling output over time, the device 5 provides an actuation signal 25 for the pump 7 so that the conveying capacity of the pump 7 can be controlled.

(8) The method 24 carried out by the device 5 is shown in the form of a block diagram in FIG. 2. In a method step 29, the method involves maintaining the inlet temperature of the charge gas in a heat exchanger that is configured to exchange heat between the charge gas and the coolant. In a method step 31, the method involves determining a target cooling output on the basis of the inlet temperature of the charge gas and on the basis of the target outlet temperature (T22.sub.target) of the charge gas coming from the heat exchanger. In a method step 33, the method involves determining a change of the target cooling output over time, and in a method step 35, the method involves providing an actuation signal for the pump on the basis of the target cooling output and on the basis of the change of the target cooling output over time.

(9) In order to prevent the coolant of the charge gas cooling circuit 3 from overheating as well as from boiling dry, the pump duty factor of the actuation signal 25 for the pump 7 has to be raised at the earliest point in time. According to an embodiment of the present invention, the pump duty factor is raised by means of the filtered derivation of the target cooling output 21. In this manner, the filtered time-related derivation of the target cooling output can define the pump duty factor, especially the actuation signal 25.

(10) The device 5 can comprise the modules that are schematically illustrated in FIG. 3 (e.g. software and/or hardware modules 37, 39 and 41) as well as the addition element 43. The feedforward control module 37 receives input signals 45, the control module 41 receives input signals 47 and the correction module 39 receives input signals 49. In particular, the input signals 45, 47 and 49 can be similar or identical input signals. The input signals 49 especially are a signal 51 of the inlet temperature of the charge gas 9, a signal 53 of the target outlet temperature (T22.sub.target) of the charge gas 15 coming from the heat exchanger 13, a signal 55 of the gas mass flow of the charge gas 9 or 15, a signal 57 of a correction (for example, of the T22 control deviation or of the temperature differential between the ambient temperature and T22.sub.target) as well as a signal 59 of an ambient air temperature.

(11) The feedforward control module 37 can also receive a target cooling output as the input signal. In particular, the control module 41 can have a PID controller which determines an output signal in such a way that the difference between the target outlet temperature (T22.sub.target) and the actual outlet temperature (T22) of the charge gas 15 becomes minimal.

(12) On the basis of the target cooling output 21 and on the basis of an ambient temperature (known from signal 59), the feedforward control module ascertains a first signal 61 which rises especially as the target cooling output 21 increases. The control module 41 determines a second signal 63 on the basis of the difference between the target outlet temperature (T22.sub.target) of the charge gas 15 and the actual outlet temperature (T22) of the charge gas 15 coming from the heat exchanger 13. The correction module 39 determines a third signal 65 on the basis of the filtered change 23 of the target cooling output 21 over time. The first signal 61, the second signal 63 and the third signal 65 are added by means of the addition element 43 in order to obtain the actuation signal 25 that is then supplied to the pump 7.

(13) FIG. 4 schematically illustrates an embodiment of the correction module 39 which (e.g. together with the modules 37 and 41) can be present in the device 5.

(14) A subtraction element 67 subtracts a target outlet temperature (signal 53, T22.sub.target) from an input signal 51 of the inlet temperature of the charge gas 9. A multiplication element 69 multiplies the result by a signal 55 of the gas mass flow. The result of the multiplication is the target cooling output 21. The derivation and filtering module 71 determines a filtered time derivation 24 of the target cooling output from the target cooling output 21, especially from a time curve of the target cooling output, or else from a sequence of target cooling outputs that correspond to several points in time. For this purpose, the processing module 71 receives as input a corrected signal 59 of the ambient temperature that has been corrected by means of a dynamic correction 73. Moreover, the derivation and filtering module 71 receives as input additional parameters 75 for the configuration of the derivation and filtering module 71. Like the dynamic correction 73, the parameters 75 can vary as a function of the ambient temperature. The filtered change 24 of the target cooling output 21 over time is entered together with the signal 57 of a correction factor into the basic engine characteristic map 77 which essentially undertakes a one-dimensional mapping from the filtered change 24 of the target cooling output 21 over time and from the correction input 57. The product from the basic engine characteristic map 77 is multiplied by means of a multiplication element 79 with the signal 59 of the ambient temperature after it has been modified by an amplitude correction element 81. In FIG. 3, the product from the multiplication element 79 represents the pump actuation signal 25 or the addition element 65.

(15) The heat exchanger 13 can be an intake pipe-integrated charge air cooler. The inlet temperature (signal 51) of the charge gas 9 does not have to be measured, but rather, it can be estimated or determined through simulation. The conveying pump 7 can also be gradient-limited so that a change of the conveying capacity of the conveying pump 7 is kept below a gradient threshold. The inlet temperature T21 of the charge gas can be, for example, between 180 C. and 100 C. The target outlet temperature T22.sub.target can be, for instance, between 10 C. and 55 C., especially approximately 45 C. The maximum temperature of the coolant before it simmers or boils can be about 130 C. The gas mass flow (signal 55) can vary by a factor of up to 10 within 100 ms, for example, in a dynamic driving range. According to an embodiment of the present invention, the temperature of the coolant does not have to be measured directly, but rather, it is estimated on the basis of the ambient temperature.

LIST OF REFERENCE NUMERALS

(16) 1 charge gas cooling system 3 charge gas cooling circuit 5 device for controlling the coolant conveying pump 7 coolant conveying pump 9 incoming charge gas 11 line sections 13 heat exchanger 14 conveying direction (can also run in the opposite direction) 15 outgoing charge gas 17 low-temperature cooler 19 signal of the gas inlet temperature 21 target cooling output 23 change of the target cooling output over time 24 filtered change of the target cooling output over time 24 actuation signal for the conveying pump 27 method 29, 31, 33, 35 method steps 37 first module 41 second module 39 third module 43 addition element 45, 47, 49 input signals 51 signal of the inlet temperature of the charge gas 53 signal of the target outlet temperature 55 signal of the charge gas mass flow 57 signal of a correction 59 signal of the ambient temperature 61 first signal 63 second signal 65 third signal 67 subtraction element 69 multiplication element 71 filtering and derivation module 73 dynamic correction 75 input parameter 77 basic engine characteristic map 70 multiplication element 81 amplitude correction